Methods And Apparatus For Monitoring A Level Of A Regulated Source

ABSTRACT

A monitor circuit for monitoring a level of a first and second regulated source may monitor a voltage level of regulated voltages or a current level of regulated currents. In an embodiment, the monitor circuit includes circuitry responsive to a first regulated voltage and to a second regulated voltage. A first circuit responsive to the first regulated voltage and to the second regulated voltage generates a first error signal indicative of at least one of an overvoltage condition of the first regulated voltage and an undervoltage condition of the second regulated voltage. A second circuit responsive to the first regulated voltage and to the second regulated voltage generates a second error signal indicative of at least one of an undervoltage condition of the first regulated voltage and an overvoltage condition of the second regulated voltage. A method for monitoring the levels of first and second regulated sources is also provided.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 14/748,692 filed on Jun. 24, 2015, which is incorporated herein byreference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable.

FIELD

This disclosure relates generally to circuits, and, more particularly,to monitor circuits and related techniques for monitoring a voltagelevel of regulated voltages and/or a current level of regulatedcurrents.

BACKGROUND

As is known, electronic circuits are used in a variety of applications.One example application is in sensing applications where a circuitincluding one or more sensing elements (e.g., pressure sensing elements,temperature sensing elements, light sensing elements, acoustic sensingelements, and magnetic field sensing elements) is used to detect one ormore parameters (e.g., pressure, temperature, light, sound, magneticfield). Magnetic field sensors, for example, are circuits including oneor more magnetic field sensing elements, generally in combination withother circuit components (e.g., analog, digital and/or mixed signalcomponents), and are used to detect a magnetic field.

In motion (e.g., rotation) detectors, for example, a magnetic fieldsensor may used to detect motion of an object, such as a ferromagneticobject, for example, a gear or ring magnet. A magnetic field associatedwith the object is typically detected by one or more magnetic fieldsensing elements, such as a Hall effect elements or a magnetoresistanceelements (e.g., giant magnetoresistance (GMR) elements), which provide asignal (i.e., a magnetic field signal) proportional to a detectedmagnetic field. One example motion detector is described in U.S. Pat.No. 8,624,588 entitled “Apparatus and Method for Providing an OutputSignal Indicative of a Speed of Rotation and a Direction of Rotation asa Ferromagnetic Object,” which is assigned to the assignee of thepresent disclosure and incorporated herein by reference in its entirety.

The magnetic field sensing elements and other circuitry may havedifferent power requirements and, thus, may be powered by signals (e.g.,voltage or current signals) of varying levels (e.g., voltage or currentlevels) as may be generated by one or more signal sources (e.g., voltageor current regulators). Some magnetic field sensor integrated circuits(ICs) contain signal regulation circuitry and methods to providesubstantially fixed output signals (e.g., voltage or current signals) topower the magnetic field sensing elements and other circuit components.

In high precision applications such as automobiles, accuracy variationsin the detected motion of a target object (e.g., resulting fromirregularities in a sensed target profile of the target object) can beproblematic. Engine ignition timing, for example, depends on consistentdetection accuracy. As one example, when magnetic field sensing elementsand other circuitry of a magnetic field sensor IC are not poweredproperly, for example, detection accuracy of the magnetic field sensorIC can be negatively impacted. Furthermore, in safety criticalapplications such as automobiles, compliance with standards such asAutomotive Safety Integrity Level (ASIL) standards, generally requiresafety mechanisms to ensure proper circuit operation.

SUMMARY

The present disclosure provides circuitry and associated methods capableof monitoring a voltage level of regulated voltages and/or a currentlevel of regulated currents. The described circuitry and methods candetect errors (e.g., overvoltage conditions, undervoltage conditions,overcurrent conditions and/or undercurrent conditions) in regulatedvoltages and/or regulated currents as may be generated by one or morevoltage sources and/or current sources, for example, and provide anindication of the detected errors through one or more error signals.

In one aspect, a monitor circuit for monitoring a voltage level of afirst regulated voltage and a second regulated voltage includescircuitry responsive to the first regulated voltage and to the secondregulated voltage. A first circuit responsive to the first regulatedvoltage and to the second regulated voltage generates a first errorsignal indicative of at least one of an overvoltage condition of thefirst regulated voltage and an undervoltage condition of the secondregulated voltage. A second circuit responsive to the first regulatedvoltage and to the second regulated voltage generates a second errorsignal indicative of at least one of an undervoltage condition of thefirst regulated voltage and an overvoltage condition of the secondregulated voltage.

The monitor circuit may include one or more of the following features.The first circuit may be powered by the first regulated voltage and thesecond circuit may be powered by the second regulated voltage. The firstregulated voltage may be generated by a first regulator and the secondregulated voltage may be generated by a second regulator. The firstcircuit may include a first comparator having a first input responsiveto the first regulated voltage and a second input responsive to thesecond regulated voltage. The second circuit may include a secondcomparator having a first input responsive to the second regulatedvoltage and a second input responsive to the first regulated voltage.The first circuit may include a first resistor divider coupled to thefirst regulated voltage to generate a first voltage and a firstcomparator having a first input responsive to the first voltage and asecond input responsive to the second regulated voltage.

The second circuit may include a second resistor divider coupled to thesecond regulated voltage to generate a second voltage and a secondcomparator having a first input responsive to the second voltage and asecond input responsive to the first regulated voltage. The firstresistor divider and the second resistor divider may be substantiallythe same. At least one of the first and second comparators may havehysteresis. The first regulated voltage and the second regulated voltagemay be substantially the same. The monitor circuit may be provided on anintegrated circuit. The integrated circuit may be a magnetic fieldsensor. The magnetic field sensor may include at least one Hall effectelement. The at least one Hall effect element may be a planar Hallelement, a vertical Hall element, or a Circular Vertical Hall (CVH)element. The magnetic field sensor may include at least onemagnetoresistance element. The at least one magnetoresistance elementmay be an anisotropic magnetoresistance (AMR) element, a giantmagnetoresistance (GMR) element, a tunneling magnetoresistance (TMR)element, a magnetic tunnel junction (MTJ) element, or a spin valveelement. The integrated circuit may include a controller responsive tothe first error signal and the second error signal to generate an erroroutput signal indicative of one or more of the overvoltage condition ofthe first regulated voltage, the undervoltage condition of the secondregulated voltage, the undervoltage condition of the first regulatedvoltage, and the overvoltage condition of the second regulated voltage.The monitor circuit and at least one of the first regulator and thesecond regulator may be provided on an integrated circuit.

In another aspect, a method for monitoring a voltage level of a firstregulated voltage and a second regulated voltage includes comparing thefirst regulated voltage to the second regulated voltage to generate afirst error signal indicative of at least one of an overvoltagecondition of the first regulated voltage and an undervoltage conditionof the second regulated voltage. The method additionally includescomparing the second regulated voltage to the first regulated voltage togenerate a second error signal indicative of at least one of anundervoltage condition of the first regulated voltage and an overvoltagecondition of the second regulated voltage.

In yet another aspect, a monitor circuit for monitoring a voltage levelof a first regulated voltage and a second regulated voltage includesmeans for generating a first error signal in response to monitoring thevoltage level of the first regulated voltage and the second regulatedvoltage. The first error signal may be indicative of at least one of anovervoltage condition of the first regulated voltage and an undervoltagecondition of the second regulated voltage. The monitor circuitadditionally includes means for generating a second error signal inresponse to monitoring the voltage level of the first regulated voltageand the second regulated voltage. The second error signal may beindicative of at least one of an undervoltage condition of the firstregulated voltage and an overvoltage condition of the second regulatedvoltage.

In yet another aspect, a monitor circuit for monitoring a voltage levelof a first regulated voltage and a second regulated voltage includes atleast two multiplexers. Each of the at least two multiplexer has a firstinput responsive to the first regulated voltage, a second inputresponsive to the second regulated voltage, and a third input responsiveto a threshold voltage and an output at which a selected one of thefirst regulated voltage, the second regulated voltage and the thresholdvoltage is provided. The monitor circuit additionally includes acomparator having a first input responsive to the output of a first oneof the multiplexers, a second input responsive to the output of a secondone of the multiplexers, and an output at which an error signal isprovided. The error signal may be indicative of a selected one of anovervoltage condition of the first regulated voltage, an undervoltagecondition of the second regulated voltage, an undervoltage condition ofthe first regulated voltage, and an overvoltage condition of the secondregulated voltage.

The monitor circuit may include one or more of the following features.The comparator may be powered by a third regulated voltage. Thethreshold voltage may be generated from the third regulated voltage. Theoutput of the multiplexers may be controlled by one or more controlsignals received from a controller. The first regulated voltage may begenerated by a first regulator and the second regulated voltage may begenerated by a second regulator. The monitor circuit may be provided onan integrated circuit. The integrated circuit may be a magnetic fieldsensor. The magnetic field sensor may include at least one Hall effectelement. The at least one Hall effect element may be a planar Hallelement, a vertical Hall element, or a Circular Vertical Hall (CVH)element. The magnetic field sensor may include at least onemagnetoresistance element. The at least one magnetoresistance elementmay be an anisotropic magnetoresistance (AMR) element, a giantmagnetoresistance (GMR) element, a tunneling magnetoresistance (TMR)element, a magnetic tunnel junction (MTJ) element, or a spin valveelement.

In yet another aspect, a monitor circuit for monitoring a current levelof a first regulated current and a second regulated current includescircuitry responsive to the first regulated current and to the secondregulated current. A first circuit responsive to the first regulatedcurrent and to the second regulated current generates a first errorsignal indicative of at least one of an overcurrent condition of thefirst regulated current and an undercurrent condition of the secondregulated current. A second circuit responsive to the first regulatedcurrent and to the second regulated current generates a second errorsignal indicative of at least one of an undercurrent condition of thefirst regulated current and an overcurrent condition of the secondregulated current.

The monitor circuit may include one or more of the following features.The first circuit may be powered by a first regulated voltage and thesecond circuit may be powered by a second regulated voltage. The firstregulated current may be generated by a first current source and thesecond regulated current may be generated by a second current source.The first circuit may include a first comparator having a first inputresponsive to the first regulated current and a second input responsiveto the second regulated current. The second circuit may include a secondcomparator having a first input responsive to the second regulatedcurrent and a second input responsive to the first regulated current.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the disclosure, as well as the disclosureitself may be more fully understood from the following detaileddescription of the drawings, which:

FIG. 1 is a block diagram of an example integrated circuit including amonitor circuit for monitoring a level of regulated sources, such as avoltage level of regulated voltages and/or a current level of regulatedcurrents;

FIG. 2 is a block diagram of an example monitor circuit of theintegrated circuit of FIG. 1;

FIG. 3 shows illustrative signal waveforms as may be generated by themonitor circuit of FIG. 2 in response to an error in a regulatedvoltage;

FIG. 3A shows illustrative signal waveforms as may be generated by themonitor circuit of FIG. 2 in response to a different error in aregulated voltage;

FIG. 3B shows illustrative signal waveforms as may be generated by themonitor circuit of FIG. 2 in response to a still different error in aregulated voltage;

FIG. 3C shows illustrative signal waveforms as may be generated by themonitor circuit of FIG. 2 in response to yet another error in aregulated voltage;

FIG. 4 is a block diagram of an example integrated circuit for detectingmotion of an object, the integrated circuit including the monitorcircuit of FIG. 2; and

FIG. 5 is a block diagram of an example monitor circuit in accordancewith another embodiment.

DETAILED DESCRIPTION

The features and other details of the disclosure will now be moreparticularly described. It will be understood that any specificembodiments described herein are shown by way of illustration and not aslimitations of the concepts, systems and techniques described herein.The principal features of this disclosure can be employed in variousembodiments without departing from the scope of the concepts sought tobe protected.

For convenience, certain introductory concepts and terms used in thespecification are collected here.

As used herein, the term “magnetic field sensor” is used to describe acircuit that uses a magnetic field sensing element, generally incombination with other circuits. Magnetic field sensors are used in avariety of applications, including, but not limited to, an angle sensorthat senses an angle of a direction of a magnetic field, a currentsensor that senses a magnetic field generated by a current carried by acurrent-carrying conductor, a magnetic switch that senses the proximityof a ferromagnetic object, a rotation detector that senses passingferromagnetic articles, for example, magnetic domains of a ring magnetor a ferromagnetic target (e.g., gear teeth) where the magnetic fieldsensor is used in combination with a back-biased or other magnet, and amagnetic field sensor that senses a magnetic field density of a magneticfield.

As used herein, the term “magnetic field sensing element” is used todescribe a variety of electronic elements that can sense a magneticfield. The magnetic field sensing element can be, but is not limited to,a Hall effect element, a magnetoresistance element, or amagnetotransistor. As is known, there are different types of Hall effectelements, for example, a planar Hall element, a vertical Hall element,and a Circular Vertical Hall (CVH) element. As is also known, there aredifferent types of magnetoresistance elements, for example, asemiconductor magnetoresistance element such as Indium Antimonide(InSb), a giant magnetoresistance (GMR) element, for example, a spinvalve, an anisotropic magnetoresistance element (AMR), a tunnelingmagnetoresistance (TMR) element, and a magnetic tunnel junction (MTJ).The magnetic field sensing element may be a single element or,alternatively, may include two or more magnetic field sensing elementsarranged in various configurations, e.g., a half bridge or full(Wheatstone) bridge. Depending on the device type and other applicationrequirements, the magnetic field sensing element may be a device made ofa type IV semiconductor material such as Silicon (Si) or Germanium (Ge),or a type III-V semiconductor material like Gallium-Arsenide (GaAs) oran Indium compound, e.g., Indium-Antimonide (InSb).

As used herein, the term “processor” is used to describe an electroniccircuit that performs a function, an operation, or a sequence ofoperations. The function, operation, or sequence of operations can behard coded into the electronic circuit or soft coded by way ofinstructions held in a memory device. A “processor” can perform thefunction, operation, or sequence of operations using digital values orusing analog signals.

In some embodiments, the “processor” can be embodied, for example, in aspecially programmed microprocessor, a digital signal processor (DSP),or an application specific integrated circuit (ASIC), which can be ananalog ASIC or a digital ASIC. Additionally, in some embodiments the“processor” can be embodied in configurable hardware such as fieldprogrammable gate arrays (FPGAs) or programmable logic arrays (PLAs). Insome embodiments, the “processor” can also be embodied in amicroprocessor with associated program memory. Furthermore, in someembodiments the “processor” can be embodied in a discrete electroniccircuit, which can be an analog circuit, a digital circuit or acombination of an analog circuit and a digital circuit. The “controller”described herein may be provided as a “processor.”

As used herein, the term “motion” is used to describe a variety of typesof movement associated with an object, for example, including rotationalmovement (or “rotation”) and linear (or “rectilinear”) movement of theobject. A “motion detector” may, for example, detect rotation of anobject. A “rotation detector” is a particular type of “motion detector.”

While a magnetic field sensor including a single magnetic field sensingelement is described in an example below, a single magnetic fieldsensing element is discussed to promote simplicity, clarity andunderstanding in the description of the concepts, systems, circuits andtechniques sought to be protected herein and is not intended to be, andshould not be construed as, limiting. The concepts, circuits andtechniques disclosed herein may, of course, be implemented using morethan a single magnetic field sensing element.

Additionally, while circuits including a first regulator and a secondregulator are described in several examples below, first and secondregulators (e.g., voltage regulators) are discussed to promotesimplicity, clarity and understanding in the description of theconcepts, systems, circuits and techniques sought to be protected hereinand is not intended to be, and should not be construed as, limiting. Theconcepts, systems, circuits and techniques disclosed herein may, ofcourse, be implemented using more than first and second regulators.Moreover, in some embodiments the first and second regulators may beprovided as part of a single regulator with the single regulatorconfigured to output two or more regulated signals (e.g., a firstregulated signal and a second regulated signal).

Further, while monitor circuits for monitoring a voltage level of afirst regulated voltage and a second regulated voltage and/or a currentlevel of a first regulated current and a second regulated current aredescribed in several examples below, first and second regulated voltagesand first and second regulated currents are discussed to promotesimplicity, clarity and understanding in the description of theconcepts, systems, circuits and techniques sought to be protected hereinand is not intended to be, and should not be construed as, limiting. Themonitor circuits disclosed herein may, of course, be implemented tomonitor more than first and second regulated voltages and more thanfirst and second regulated currents.

Referring to FIG. 1, a circuit 100 capable of monitoring a voltage levelof voltage signals and/or a current level of current signals is shown.The circuit 100 includes a first source 110 and a second source 120,each of which may take a variety of forms. For example, the first source110 and the second source 120 may take the form of a voltage regulatorand may be provided as a linear regulator (e.g., NPN Darlington orLow-dropout (LDO) regulator) or a switching regulator (e.g., Buck,Buck-boost, or Boost regulator), as a few examples. The first source 110generates a first regulated voltage 110 a and the second source 120generates a second regulated voltage 120 a. In some embodiments, thefirst regulated voltage 110 a and the second regulated voltage 120 a aresubstantially the same (i.e., same fixed output voltages). In otherembodiments, the first regulated voltage 110 a and the second regulatedvoltage 120 a are different.

The circuit 100 also includes a monitor circuit 130 for monitoring avoltage level of the first regulated voltage 110 a and the secondregulated voltage 120 a. In the example embodiment shown, the monitorcircuit 130 is coupled to receive the first regulated voltage 110 agenerated by the first source 110 and the second regulated voltage 120 agenerated by the second source 120 and configured to generate a firstsignal 130 a, which in some embodiments is representative of a firsterror, or fault signal indicative of at least one of an overvoltagecondition (e.g., a higher than expected voltage level) of the firstregulated voltage 110 a and an undervoltage condition (e.g., a lowerthan expected voltage level) of the second regulated voltage 120 a. Themonitor circuit 130 is further configured to generate a second signal130 b, which in some embodiments is representative of a second error, orfault signal indicative of at least one of an undervoltage condition ofthe first regulated voltage 110 a and an overvoltage condition of thesecond regulated voltage 120 a.

The circuit 100 additionally includes a controller 140 coupled toreceive the first signal 130 a and the second signal 130 b andconfigured to generate a controller output signal 140 a. The controlleroutput signal 140 a may be provided as an error output signal indicativeof one or more of the overvoltage condition of the first regulatedvoltage, the undervoltage condition of the second regulated voltage, theundervoltage condition of the first regulated voltage, and theovervoltage condition of the second regulated voltage. Additionally, insome embodiments, the controller output signal 140 a is received bycircuitry (e.g., analog, digital or mixed-signal circuitry) configuredto generate corresponding signals (e.g., filtered signals, amplifiedsignal, and the like).

In an alternative embodiment, the circuit 100 is additionally oralternatively capable of monitoring a current level of current signalsand the first source 110 and the second source 120 take the form of acurrent regulator. As one example, the first source 110 may generate afirst regulated current and the second source 120 may generate a secondregulated current. The monitor circuit 130 may monitor a current levelof the first regulated current and the second regulated current andgenerate a first signal, which in some embodiments is representative ofa first error, or fault signal indicative of at least one of anovercurrent condition (e.g., a higher than expected current level) ofthe first regulated current and an undercurrent condition (e.g., a lowerthan expected current level) of the second regulated current. Themonitor circuit 130 may also generate a second signal, which in someembodiments is representative of a second error, or fault signalindicative of at least one of an undercurrent condition of the firstregulated current and an overcurrent condition of the second regulatedcurrent.

It will be appreciated that the circuit 100 may take any form of circuitwhich would benefit from monitoring of a voltage level and/or a currentlevel of signals. For example, the circuit 100 can be provided in theform of an integrated circuit such as a digital integrated circuit,analog integrated circuit, or a mixed-signal integrated circuit andrepresentative of a sensor integrated circuit containing sensorcircuitry. As one example, the circuit 100 may be a magnetic fieldsensor integrated circuit that contains one or more magnetic fieldsensing elements and that provides an output signal indicative of amagnetic field, as will be discussed further below.

Referring to FIG. 2, in which like elements of FIG. 1 are shown havinglike reference designations, the monitor circuit 130 is coupled toreceive the first regulated level 110 a at a first terminal 210 and thesecond regulated level 120 a at a second terminal 220. In an embodiment,the first regulated level 110 a is a regulated voltage level that can begenerated by a first regulator, which can be the same as or similar tothe source 110 (FIG. 1), and the second regulated level 120 a is aregulated voltage level that can be generated by a second regulator,which can be the same as or similar to the source 120 (FIG. 1). In someembodiments, the first regulated voltage 110 a and the second regulatedvoltage 120 a can be generated by a single source (not shown).

The monitor circuit 130 includes a first circuit including a firstresistor divider, as indicated by R1, R2 and R3, and a first comparator132. The first resistor divider is coupled between the first terminal210 of the monitor circuit 130 and a reference potential (e.g., GND).The value of resistors R1, R2 and R3 and the ratio of the values ofresistors R1, R2 and R3 can, for example, be chosen based on a voltagelevel associated with the first regulated voltage 110 a and/or apredetermined range of voltages of the first regulated voltage 110 a.

The first comparator 132 is coupled to receive a voltage associated withthe first resistor divider (e.g., a level shifted voltage) at a firstcomparator input (e.g., an inverting input) and a voltage associatedwith the second regulated voltage 120 a at a second comparator input(e.g., a non-inverting input) and is configured to generate a firstcomparison signal (e.g., a first error signal) 130 a in response to thefirst comparator input and the second comparator input. The firstcomparison signal 130 a may have edges occurring in response to acomparison of the first comparator input and the second comparatorinput. In the embodiment shown in FIG. 2, when the voltage at the firstcomparator input is greater than the voltage at the second comparatorinput, the first comparator output (i.e., the first comparison signal130 a) is at a logic low level and when the voltage at the firstcomparator input is less than the voltage at the second comparatorinput, the first comparator output (i.e., the first comparison signal130 a) is at a logic high level.

The monitor circuit 130 additionally includes a second circuit having asecond resistor divider, as indicated by R4, R5 and R6, and a secondcomparator 134. The second resistor divider, which can be the same as orsimilar to the first resistor divider in some embodiments, is coupledbetween the second terminal 220 of the monitor circuit 130 and areference potential (e.g., GND). Similar to resistors R1, R2 and R3 ofthe first resistor divider, the value of resistors R4, R5 and R6 and theratio of the values of resistors R4, R5 and R6 can be chosen based on avoltage level associated with the second regulated voltage 120 a and/ora predetermined range of voltages of the second regulated voltage 120 a.

The second comparator 134, which can be the same as or similar to firstcomparator 132, is coupled to receive a voltage associated with thesecond resistor divider at a first comparator input (e.g., an invertinginput) and a voltage associated with the first regulated voltage 110 aat a second comparator input (e.g., a non-inverting input) and isconfigured to generate a second comparison signal (e.g., a second errorsignal) 130 b in response to the first comparator input and the secondcomparator input. Similar to first comparison signal 130 a, the secondcomparison signal 130 b may have edges occurring in response to acomparison of the first comparator input and the second comparatorinput. In the embodiment shown in FIG. 2, when the voltage at the firstcomparator input of the second comparator 134 is greater than thevoltage at the second comparator input, the second comparator output(i.e., the second comparison signal 130 b) is at a logic low level andwhen the voltage at the first comparator input is less than the voltageat the second comparator input, the second comparator output (i.e., thesecond comparison signal 130 b) is at a logic high level.

In the embodiment in which the first regulated level 110 a is aregulated voltage and the second regulated level 120 a is a regulatedvoltage, the first comparator 132 may be powered by the first regulatedvoltage 110 a (as is represented by the dotted line from regulatedvoltage 110 a to power comparator 132) and the second comparator 134 maybe powered by the second regulated voltage 120 a (as is represented bythe dotted line from regulated voltage 120 a to power comparator 134).

In some embodiments, at least one of the first resistor divider and thesecond resistor divider are optional, in which case a first one of thecomparator inputs of the first and/or second circuits may be coupled tothe first regulated voltage and a second one of the second comparatorinputs of the first and/or second circuits may be coupled to the secondregulated voltage.

Additionally, in some embodiments, at least one of the first comparator132 and the second comparator 134 has hysteresis. The hysteresis can beselected based on a voltage condition to be detected, such as anovervoltage condition or an undervoltage condition, as will be explainedbelow.

While various factors may be considered in selecting the first resistordivider, the second resistor divider, and comparator hysteresis, forexample, in some embodiments these selections are made to cause thefirst comparison signal 130 a to transition when the second regulatedvoltage 120 a falls below a predetermined level indicative of anundervoltage condition of the second regulated voltage 120 a and thefirst comparison signal 130 a to transition when the first regulatedvoltage 110 a goes above a predetermined level indicative of anovervoltage condition of the first regulated voltage 110 a.Additionally, in some embodiments, these selections are made to causethe second comparison signal 130 b to transition when the firstregulated voltage 110 a falls below a predetermined level indicative ofan undervoltage condition of the first regulated voltage 110 a and thesecond comparison signal 130 b to transition when the second regulatedvoltage 120 a goes above a predetermined level indicative of anovervoltage condition of the second regulated voltage 120 a.

In an alternative embodiment, the monitor circuit 130 is coupled toreceive a first regulated current at the first terminal 210 and a secondregulated current at the second terminal 220. As one example, the firstcomparator 132 may be coupled to receive a voltage proportional tocurrent (e.g., the first regulated current) flowing through the firstresistor divider at the first comparator input (e.g., an invertinginput) and a voltage proportional to current (e.g., the second regulatedcurrent) flowing through the second resistor divider at the secondcomparator input (e.g., a non-inverting input) and may be configured togenerate the first comparison signal (e.g., a first error signal) 130ain response to the first comparator input and the second comparatorinput. The first comparator 132 may be powered by a first voltage (e.g.,a first regulated voltage) as may be generated by a first voltage source(not shown), which may be provided as part of or separate from thecircuit 100 (FIG. 1).

Additionally, the second comparator 134 may be coupled to receive avoltage proportional to current (e.g., the second regulated current)flowing through the second resistor divider at the first comparatorinput (e.g., an inverting input) and a voltage proportional to current(e.g., the first regulated current) flowing through the first resistordivider at the second comparator input (e.g., a non-inverting input) andmay be configured to generate the second comparison signal (e.g., afirst error signal) 130 b in response to the first comparator input andthe second comparator input. The second comparator 134 may be powered bya second voltage (e.g., a second regulated voltage), which may be thesame as or similar to the first voltage. Additionally, the secondvoltage may be generated by a second voltage source (not shown), whichmay be the same as or similar to the first voltage source. In someembodiments, both the first voltage and the second voltage are generatedby a same voltage source.

One or more of the first resistor divider, the second resistor divider,and/or comparator hysteresis in the monitor circuit 130 may be selectedto cause the first comparison signal 130 a to transition when the secondregulated current falls below a predetermined level indicative of anundercurrent condition of the second regulated current and the firstcomparison signal 130 a to transition when the first regulated currentgoes above a predetermined level indicative of an overcurrent conditionof the first regulated current. Additionally, in some embodiments, theseselections may be made to cause the second comparison signal 130 b totransition when the first regulated current falls below a predeterminedlevel indicative of an undercurrent condition of the first regulatedcurrent and the second comparison signal 130 b to transition when thesecond regulated current goes above a predetermined level indicative ofan overcurrent condition of the second regulated current.

With the described circuits and techniques, two regulated voltagesand/or two regulated currents are monitored in real-time for bothovervoltage and undervoltage conditions and/or for both overcurrent andundercurrent conditions, respectively, with only two comparators (ratherthan four comparators as would generally be required to detect fourdifferent error conditions). This resulting reduction in the number ofdevices required for error detection is generally advantageous becauseof space and cost considerations as well as the advantage of havingfewer devices to potentially fail. The space considerations areparticularly advantageous in embodiments in which the circuitry isprovided in the form of an integrated circuit. Furthermore, thedescribed regulated voltage monitoring arrangement permits such faultmonitoring of two regulated voltages without requiring an additional,third, regulated voltage to power the monitoring circuitry.

Referring to FIGS. 3-3C, illustrative signal waveforms as may begenerated by a plurality of regulators, which can be the same as orsimilar to first and second sources 110, 120 shown in FIG. 1, andillustrative signal waveforms as may be generated by a monitor circuit,which can be the same as or similar to monitor circuit 130 shown in FIG.2, are shown in a plurality of plots (e.g., 310, 320, 330, 340, shown inFIG. 3). While the illustrative waveforms are associated with use of themonitor circuit 130 to monitor first and second regulated voltages fromfirst and second respective voltage regulators, it will be appreciatedthat similar waveforms can be associated with use of the monitor circuitto monitor first and second current levels from first and secondrespective regulated current sources. The plots have a horizontal axiswith a scale in time units and a vertical axis with a scale in voltageunits of volts (V). Each of FIGS. 3-3C shows a first regulated voltagesignal representative of an example first regulated voltage (e.g., 110a, shown in FIG. 1) generated by a regulator (e.g., 110, shown in FIG.1), for example and a second regulated voltage signal representative ofan example second regulated voltage (e.g., 120 a, shown in FIG. 1)generated by a regulator (e.g., 120, shown in FIG. 1), for example. Eachof FIGS. 3-3C also shows a first comparison signal representative of anexample first comparison signal (e.g., 130 a, shown in FIG. 2) generatedby the monitor circuit and a second comparison signal 320 arepresentative of an example second comparison signal (e.g., 130 b,shown in FIG. 2) generated by the monitor circuit. The first comparisonsignal, which in some cases can be representative of a first errorsignal, can be generated by a first example comparator (e.g., 132, shownin FIG. 2) and the second comparison signal, which in some cases can berepresentative of a second error signal, can be generated by a secondexample comparator (e.g., 134, shown in FIG. 2).

Referring to FIG. 3, a plot 310 includes a signal 310 a representativeof a first regulated voltage signal, a plot 320 includes a signal 320 arepresentative of a second comparison signal, a plot 330 includes asignal 330 a representative of a second regulated voltage signal and aplot 340 includes a signal 340 a representative of a first comparisonsignal. In the example embodiment shown, at least signal 320 a andsignal 340 a are provided as digital signals having a logic high leveland a logic low level. It will be appreciated, however, that theparticular delineation of which signals are provided as analog signalsand digital signals can be varied.

As illustrated, when signal 310 a has a voltage level that is greaterthan a voltage level of signal 330 a, signal 340 a is at a logic lowlevel (or, transitions from a logic high level to a logic low level). Asone example, this set of conditions may be representative of anovervoltage condition of signal 310 a (i.e., an overvoltage condition ofthe first regulated signal). As is also illustrated, when signal 310 ahas a voltage level that is less than a voltage level of signal 330 a,signal 340 a is at a logic high level (or, transitions from a logic lowlevel to a logic high level).

Further, as illustrated, signal 320 a is at a logic high level whensignal 310 a has a voltage level that is greater than a voltage level ofsignal 330 a and signal 320 a is at a logic low level when signal 310 ahas a voltage level that is less than a voltage level of signal 330 a.In the illustrated embodiment, signal 310 a has a voltage level that isgreater than or equal to a voltage level of signal 330 a for the timeperiod shown, and thus, signal 320 a remains at a logic high level.

Referring to FIG. 3A, in which like signals of FIG. 3 are shown havinglike reference designations, a plot 312 includes a signal 310 a, a plot322 includes a signal 320 a, a plot 332 includes a signal 330 a and aplot 342 includes a signal 340 a.

As illustrated, when signal 310 a has a voltage level that is less thana voltage level of signal 330 a, signal 320 a is at a logic low level(or, transitions from a logic high level to a logic low level). As oneexample, such conditions may be representative of an undervoltagecondition of signal 310 a (i.e., an undervoltage condition of the firstregulated signal). It will be appreciated that the signal 310 a having alevel less than the level of signal 330 a can also be indicative of ashort circuit condition between the first regulated signal 110 a andground. As is also illustrated, when signal 310 a has a voltage levelthat is greater than a voltage level of signal 330 a, signal 320 a is ata logic high level (or, transitions from a logic low level to a logichigh level).

Referring to FIG. 3B, in which like signals of FIG. 3 are shown havinglike reference designations, a plot 314 includes a signal 310 a, a plot324 includes a signal 320 a, a plot 334 includes a signal 330 a and aplot 344 includes a signal 340 a.

As illustrated, when signal 310 a has a voltage level that is less thana voltage level of signal 330 a, signal 320 a is at a logic low level(or, transitions from a logic high level to a logic low level). As oneexample, such conditions may be representative of an overvoltagecondition of signal 330 a (i.e., an overvoltage condition of the secondregulated signal). It will be appreciated that the signal 330 a having alevel less than signal 310 a can also be indicative of a short circuitcondition between the second regulated signal 120 a and ground. As isalso illustrated, when signal 310 a has a voltage level that is greaterthan a voltage level of signal 330 a, signal 320 a is at a logic highlevel (or, transitions from a logic low level to a logic high level).

Referring to FIG. 3C, in which like signals of FIG. 3 are shown havinglike reference designations, a plot 316 includes a signal 310 a, a plot326 includes a signal 320 a, a plot 336 includes a signal 330 a and aplot 346 includes a signal 340 a.

As illustrated, when signal 330 a has a voltage level that is less thana voltage level of signal 310 a, signal 340 a is at a logic low level(or, transitions from a logic high level to a logic low level). As isalso illustrated, when signal 330 a has a voltage level that is greaterthan a voltage level of signal 310 a, signal 340 a is at a logic highlevel (or, transitions from a logic low level to a logic high level). Asone example, such conditions may be representative of an undervoltagecondition of signal 330 a (i.e., an undervoltage condition of the secondregulated signal).

Referring to FIG. 4, in which like elements of FIGS. 1 and 2 areprovided having like reference designations, a magnetic field sensor 400capable of detecting motion (e.g., speed of motion and/or direction ofmotion) of an object having features, e.g., gear teeth 420 a, 420 b, 420c, 420 d of a ferromagnetic gear 420 (hereinafter “object 420”), isshown. The object 420 can be disposed, for example, on a shaft 410configured to rotate in a direction 412.

The magnetic field sensor 400 includes one or more magnetic fieldsensing elements, as indicated by magnetic field sensing element 440 inthe example embodiment shown. The magnetic field sensing element 440 isdriven by a current source 430 and configured to generate a magneticfield signal 440 a in response to a magnetic field associated with theobject 420 as may be generated, for example, by a magnet 450 disposedproximate to or within the magnetic field sensor 400. Motion of theobject 420 can result in variations of the magnetic field sensed by themagnetic field sensing element 440 and, thus, result in variations ofthe magnetic field signal 440 a generated by the magnetic field sensingelement 440.

Although the magnetic field sensing element 440 is depicted as a Halleffect element, in some embodiments the magnetic field sensing element440 is, for example, provided as a magnetoresistance element where themagnetoresistance element may be an anisotropic magnetoresistance (AMR)element, a giant magnetoresistance (GMR) element, a tunnelingmagnetoresistance (TMR) element, a magnetic tunnel junction (MTJ)element, or a spin valve element. It should be appreciated that themagnetic field sensing element 440 (which may comprise more than onemagnetic field sensing element in some embodiments) may take any formsuitable for detecting motion of the object 420 by sensing a magneticfield affected by such motion.

The object 420 may be a ferromagnetic object. The ferromagnetic objectcan be a magnetic object and the magnetic field detected by the magneticfield sensing element 440 may be generated by the object 420 itself andmay vary depending on positions of the object 420 relative to themagnetic field sensor 400.

Furthermore, although the object 420 is shown in the form of aferromagnetic gear in the example embodiment, the object 420 may takeother forms. For example, the object 420 may take the form of a ringmagnet having magnetic domains that are detected by the magnetic fieldsensor 400. Additionally, the object 420 may be coupled to an automobilewheel, steering shaft, or a camshaft, as a few examples.

The magnetic field sensor 400 may be provided in the form of anintegrated circuit, which can be the same as or similar to the circuit100 described above in conjunction with FIG. 1. The sensor 400 includesa signal path 460 (e.g., an analog, digital or mixed signal path)coupled to receive the magnetic field signal 440 a and configured togenerate a signal (e.g., digital signal 466 a) representative of themagnetic field signal 440 a.

The illustrated signal path 460 includes an amplifier 462, a filter 464and an analog-to-digital converter (ADC) 466. The amplifier 462 iscoupled to receive the magnetic field signal 440 a generated by themagnetic field sensing element 440 and configured to generate anamplified signal 462 a. The filter 464, which can be a programmableanalog filter for example, is coupled to receive the amplified signal462 a and configured to generate a filtered signal 464 a. The ADC 466 iscoupled to receive the filtered signal 464 a and configured to generatea corresponding digital signal 466 a.

The magnetic field sensor 400 additionally includes a first source 110providing a first regulated voltage 110 a (or a first regulatedcurrent), a second source 120 providing a second regulated voltage 120 a(or a second regulated current), and a monitor circuit 130 similar tolike elements described above in conjunction with FIGS. 1 and 2. Thus,monitor circuit 130 is responsive to the first and second regulatedvoltages 110 a, 120 a (or to the first and second regulated currents)and generates comparison, or error signals 130 a, 130 b.

The magnetic field sensor 400 further includes a controller 470 andmemory device 480 (e.g., EEPROM). The controller 470, which can be asynchronous digital controller or an analog controller for example, iscoupled to receive at least the digital signal 466 a, the first signal130 a and the second signal 130 b. The controller 470 is responsive toat least the first signal 130 aand the second signal 130 b to generate acontroller output signal 470 a (e.g., an error signal). In someembodiments, controller output signal 470 a is indicative of one or moreof the overvoltage condition of the first regulated voltage 110 a, theundervoltage condition of the second regulated voltage 120 a, theundervoltage condition of the first regulated voltage 110 a, and theovervoltage condition of the second regulated voltage 120 a.Additionally, in embodiments where the first source 110 provides a firstregulated current and the second source provides a second regulatedcurrent, controller output signal 470 a may be indicative of one or moreof the overcurrent condition of the first regulated current, theundercurrent condition of the second regulated current, the undercurrentcondition of the first regulated current, and the overcurrent conditionof the second regulated current.

In embodiments where the controller 470 is additionally responsive tothe digital signal 466 a in generating the controller output signal 470a, for example, the controller output signal 470 a may perform gainand/or offset correction as may be achieved with a gain adjustmentprocessor and an offset adjustment processor in the controller 470.Additionally, the controller 470 can be coupled to receive stored gaincorrection coefficients and stored offset correction coefficients,respectively, from the memory device 480, with the controller outputsignal 470 a generated accordingly. It will be appreciated that thestored gain correction coefficients and the stored offset correctioncoefficients may be established in a variety of manners, such as thosedescribed in U.S. Pat. No. 8,350,563 entitled “Magnetic Field Sensor andMethod used in a Magnetic Field Sensor that Adjusts a Sensitivity and/oran Offset Over Temperature” which is assigned to the Assignee of thepresent disclosure and incorporated herein by reference in its entirety.

The controller 470 may contain or be coupled to circuitry configured togenerate a signals (e.g., motion detection output signals) indicative ofone or more of a speed of motion of the object 420 or a direction ofmotion of the object 420. One such circuit is described in co-pendingU.S. patent application Ser. No. 14/600,826 entitled “Methods AndApparatus For Generating A Threshold Signal In A Magnetic Field Sensor,”which is assigned to the Assignee of the present disclosure andincorporated herein by reference in its entirety.

While the magnetic field sensor 400 may be provided in the illustratedform of an integrated circuit with an analog front end portion and adigital portion, it will be appreciated that the particular delineationof which circuit functions are implemented in an analog fashion or withdigital circuitry and signals can be varied. Further, some of theillustrated circuit functions can be implemented on an integratedcircuit sensor and other circuitry and functionality can be implementedon separate circuits (e.g., additional substrates within the sameintegrated circuit package, or additional integrated circuit packages,and/or on circuit boards).

In some embodiments, one or more portions of the signal path 460 (e.g.,amplifier 462, filter 464, ADC 466) may be provided as part of thecontroller 470 and, thus, signal path 460 is shown in phantom.Additionally, in some embodiments, the controller 470 can perform thefunction, operation, or sequence of operations of one or more portionsof the signal path 460. Moreover, in some embodiments, the memory device480 is provided as part of the controller 470 (e.g., as onboard EEPROM).

Referring now to FIG. 5, a monitor circuit 530 in accordance withanother embodiment is shown. The monitor circuit 530, which may beprovided on an integrated circuit such as integrated circuit 100 (FIG.1), for example, is coupled to receive a first regulated voltage 510 a,which can be the same as or similar to the first regulated voltage 110 a(FIG. 1) or a particular percentage (e.g., fifty percent) of the firstregulated voltage 110 a, for example, at a first input terminal 510. Themonitor circuit 530 is also coupled to receive a second regulatedvoltage 520 a, which can be the same as or similar to the secondregulated voltage 120 a (FIG. 1) or a particular percentage (e.g., fiftypercent) of the second regulated voltage 120 a, for example, at a secondinput terminal 520. The first regulated voltage 510 a can be generatedby a first source, which can be the same as or similar to the source 110(FIG. 1), and the second regulated voltage 520 a can be generated by asecond source, which can be the same as or similar to the source 120(FIG. 1).

The monitor circuit 530 includes two or more multiplexers, for example,a first multiplexer 532 and a second multiplexer 534, as shown, eachcoupled to receive the first regulated voltage 510 a and the secondregulated voltage 520 a at respective inputs. The first multiplexer 532and the second multiplexer 534 are also coupled to receive a thresholdvoltage (VTH), for example, a first threshold voltage and a secondthreshold voltage, as shown, and to provide a selected one of the firstregulated voltage, the second regulated voltage, or and the receivedthreshold voltages at a respective output. The first threshold voltageand the second threshold voltage (e.g., voltages at nodes 531 a, 531 b)can be generated from a voltage V+, which may be provided from a thirdregulated voltage, for example. Additionally, the first thresholdvoltage and the second threshold voltage can be selected based onvarious factors, such as available voltage levels of the monitor circuit530 and/or level shifting by a resistor divider coupled between thevoltage V+ and a reference potential (GND).

The monitor circuit 530 also includes a comparator 536 coupled toreceive a signal 532 a from the output of the first multiplexer 532 at afirst comparator input (e.g., a non-inverting input) and a signal 534 afrom the output of the second multiplexer 534 at a second comparatorinput (e.g., an inverting input). The comparator 536, which is poweredby the voltage V+, receives the signal 532 a and the signal 534 a andgenerates a comparison signal 530 a that transitions in response to acomparison of the signal 532 a and the signal 534 a. The comparisonsignal 530 a, which may be the same as or similar to one or more of thefirst comparison signal 130 a (FIG. 2) and the second comparison signal130 b (FIG. 2), can be provided as an error signal indicative of aselected one of an overvoltage condition of the first regulated voltage510 a, an undervoltage condition of the second regulated voltage 520 a,an undervoltage condition of the first regulated voltage 510 a, and anovervoltage condition of the second regulated voltage 520 a.

In the example embodiment shown, the monitor circuit 530 is furthercoupled to receive one or more control signals, for example, a firstcontrol signal 540 a and a second control signal 540 b, as shown. Thefirst control signal 540 a and the second control signal 540 b may begenerated by a controller (not shown), for example, which can be thesame as or similar to controller 140 (FIG. 1). The output (i.e., signals532 a, 534 a) of each of multiplexers 532, 534 may be controlled byfirst control signal 540 a and/or the second control signal 540 b, whichsignals may be received at selector terminals S1, S2 of multiplexers532, 534.

In operation, the control signals 540 a, 540 b determine which of themultiplexer input signals are coupled to the respective multiplexeroutput and thus to the inputs of the comparator 536 to provide thecomparison signal 530 a. In one embodiment, the control signal statesand the resulting fault conditions that are detected is governed by thefollowing Table.

Control signal 540a is low Control signal 540a is high Control signalOvervoltage condition of Overvoltage condition of 540b is low regulatedvoltage 510a regulated voltage 510b (as is achieved by (as is achievedby comparing regulated comparing regulated voltage 510a tothresholdvoltage 510B to threshold voltage 531a) voltage 531a) Control signalUndervoltage condition of Undervoltage condition of 540b is highregulated voltage 510a regulated voltage 510b (as is achieved by (as isachieved by comparing regulated comparing regulated voltage 510a tothreshold voltage 510B to threshold voltage 531b) voltage 531b)

It will be appreciated that in some embodiments the monitor circuit 530may additionally or alternatively be configured to monitor a currentlevel of signals (e.g., a first regulated current and a second regulatedcurrent) in a same or similar manner to which the monitor circuit 530monitors a voltage level of the first regulated voltage 510 a and thesecond regulated voltage 520 a. As one example, the monitor circuit 530may be coupled to receive a first regulated current at the first inputterminal 510 and a second regulated current at the second input terminal520 and provide the comparison signal 530 a in response to monitoring acurrent level of the first regulated current and the second regulatedcurrent.

As described above and will be appreciated by one of skill in the art,embodiments of the disclosure herein may be configured as a system,method, or combination thereof. Accordingly, embodiments of the presentdisclosure may be comprised of various means including hardware,software, firmware or any combination thereof. Furthermore, embodimentsof the present disclosure may take the form of a computer programproduct on a computer-readable storage medium having computer readableprogram instructions (e.g., computer software) embodied in the storagemedium. Any suitable non-transitory computer-readable storage medium maybe utilized.

Having described preferred embodiments, which serve to illustratevarious concepts, structures and techniques, which are the subject ofthis patent, it will now become apparent to those of ordinary skill inthe art that other embodiments incorporating these concepts, structuresand techniques may be used. Additionally, elements of differentembodiments described herein may be combined to form other embodimentsnot specifically set forth above.

Accordingly, it is submitted that that scope of the patent should not belimited to the described embodiments but rather should be limited onlyby the spirit and scope of the following claims.

What is claimed is:
 1. A monitor circuit for monitoring a voltage levelof a first regulated voltage and a second regulated voltage, the monitorcircuit comprising: at least two multiplexers, each having a first inputresponsive to the first regulated voltage, a second input responsive tothe second regulated voltage, and a third input responsive to athreshold voltage and an output at which a selected one of the firstregulated voltage, the second regulated voltage and the thresholdvoltage is provided; and a comparator having a first input responsive tothe output of a first one of the multiplexers, a second input responsiveto the output of a second one of the multiplexers, and an output atwhich an error signal is provided, wherein the error signal isindicative of a selected one of an overvoltage condition of the firstregulated voltage, an undervoltage condition of the second regulatedvoltage, an undervoltage condition of the first regulated voltage, andan overvoltage condition of the second regulated voltage.
 2. The monitorcircuit of claim 1, wherein the comparator is powered by a thirdregulated voltage, wherein the threshold voltage is generated from thethird regulated voltage.
 3. The monitor circuit of claim 2, wherein theoutput of the multiplexers is controlled by one or more control signalsreceived from a controller.
 4. The monitor circuit of claim 1, whereinthe first regulated voltage is generated by a first regulator and thesecond regulated voltage is generated by a second regulator.
 5. Themonitor circuit of claim 1, wherein the monitor circuit is provided onan integrated circuit.
 6. The monitor circuit of claim 5, wherein theintegrated circuit is a magnetic field sensor.
 7. The monitor circuit ofclaim 6, wherein the magnetic field sensor comprises at least one Halleffect element.
 8. The monitor circuit of claim 7, wherein the at leastone Hall effect element is a planar Hall element, a vertical Hallelement, or a Circular Vertical Hall (CVH) element.
 9. The monitorcircuit of claim 6, wherein the magnetic field sensor comprises at leastone magnetoresistance element.
 10. The monitor circuit of claim 9,wherein the at least one magnetoresistance element is an anisotropicmagnetoresistance (AMR) element, a giant magnetoresistance (GMR)element, a tunneling magnetoresistance (TMR) element, a magnetic tunneljunction (MTJ) element, or a spin valve element.
 11. A monitor circuitfor monitoring a voltage level of a first regulated voltage and a secondregulated voltage, the monitor circuit comprising: a first multiplexercoupled to receive a first regulated voltage, a second regulatedvoltage, and a first threshold voltage; a second multiplexer coupled toreceive the first regulated voltage, the second regulated voltage, and asecond threshold voltage; and a comparator coupled to a first output ofthe first multiplexer and a second output of the second multiplexer, thecomparator configured to generate an error signal indicative of aselected one of an overvoltage condition of the first regulated voltage,an undervoltage condition of the second regulated voltage, anundervoltage condition of the first regulated voltage, and anovervoltage condition of the second regulated voltage.
 12. The monitorcircuit of claim 11, wherein each multiplexer is configured to provide aselected one of the first regulated voltage, the second regulatedvoltage, or the received threshold voltage at an output of therespective multiplexer.
 13. The monitor circuit of claim 11, wherein thefirst threshold voltage is different than the second threshold voltage.14. The monitor circuit of claim 11, wherein the first and secondthreshold voltages are provided by a third regulated voltage.
 15. Themonitor circuit of claim 11, wherein the monitor circuit is provided onan integrated circuit (IC), and wherein the IC is a magnetic fieldsensor.
 16. The monitor circuit of claim 15, wherein the magnetic fieldsensor comprises at least one Hall effect element or at least onemagnetoresistance element.
 17. A method for monitoring a voltage levelof a first regulated voltage and a second regulated voltage, the methodcomprising: receiving, at a first multiplexer, a first regulatedvoltage, a second regulated voltage, and a first threshold voltage;receiving, at a second multiplexer, the first regulated voltage, thesecond regulated voltage, and a second threshold voltage; receiving, atinputs of a comparator coupled to a first output of the firstmultiplexer and a second output of the second multiplexer, selected onesof the first regulated voltage, the second regulated voltage, the firstthreshold voltage, or the second threshold voltage as output by thefirst multiplexer and the second multiplexer; and comparing, by thecomparator, the first output of the first multiplexer to the secondoutput of the second multiplexer to provide an error signal indicativeof a selected one of an overvoltage condition of the first regulatedvoltage, an undervoltage condition of the second regulated voltage, anundervoltage condition of the first regulated voltage, and anovervoltage condition of the second regulated voltage.
 18. The method ofclaim 17, wherein comparing the first output to the second outputcomprises: comparing the first regulated voltage to the first thresholdvoltage to generate a first error signal indicative of an overvoltagecondition of the first regulated voltage; comparing the first regulatedvoltage to the second threshold voltage to generate a second errorsignal indicative of an undervoltage condition of the first regulatedvoltage; comparing the second regulated voltage to the first thresholdvoltage to generate a third error signal indicative of an overvoltagecondition of the second regulated voltage; and comparing the secondregulated voltage to the second threshold voltage to generate a fourtherror signal indicative of an overvoltage condition of the secondregulated voltage.